Lighting for a hydroponic gardening setup is an important choice to decide on early in the planning process. The right type of light can double your crop. There are several types of effective hydroponic grow lights available today: fluorescent, LED, metal halide, high-pressure sodium, and high-density discharge lamps. All of these lamps have their advantages and disadvantages. It all depends on what you’re growing, the shape and size of the plants and your budget. Incandescent lighting isn’t included as it is too inefficient for proper plant growth as well as energy usage.
HID Lamps
There are two subcategories of HID lamps: metal halide (MH) and high-pressure sodium (HPS). These lamp types both emit a much more intense light than standard fluorescent bulbs, which also pass electricity through a gas-filled tube. The brightest grow lights available are high-intensity discharge (HID) lights. They can be installed anywhere in your home, garage, or greenhouse to supplement existing light, and they can serve as the sole source of light for your plants. They work well, have a reasonable life expectancy and bulb prices have dropped over the years. On the downside, these bulbs create massive amounts of heat that can be difficult if not impossible to deal with in a confined space. High heat is too much for the plants confined in a grow room or tent so excess heat must be carried away or they will be damaged. On the upside, in the cool climates, the wasted heat can be redirected toward living spaces as an offset to heating costs.
Both types of HID bulbs pass current through a sealed glass or ceramic tube containing a mixture of gasses. Different gas blends will determine the light color emitted by each type of lamp. While one 400-watt HID lamp emits as much light as 800 watts of fluorescent tubing, HID lights are twice as efficient as fluorescent lamps. Most high-intensity discharge light can run on standard 120-volt household current but they require special fixtures with ballasts. When talking about bulb types and styles, it is important to understand that while we tend to buy them based on wattage, there are more important numbers that make a difference. (see post regarding lux)
Metal Halide
Metal halide bulbs, a type of HID, while less efficient than HPS bulbs, emit colors in the blue spectrum. That color we know as “cool white” would be closest. This end of the color spectrum is best used for leafy growth. Because this type of lamp doesn’t distort colors, it is relatively easy on the eyes where the garden is in a living space. MH bulbs produce roughly 60-125 lumens per watt, depending on the wattage of the bulb. Lamp life is 6,000 to 15,000 hours.
High-Pressure Sodium
High-pressure sodium bulbs are similar in style to metal halide only because of the heat they produce. The light emitted from HPS is more yellow in color but tends to distort natural colors of rooms and can be annoying in a living space. This part of the spectrum is best for flowering and fruiting stages of plant growth. HPS bulbs produce roughly 60-140 lumens per watt with an average lamp life in excess of 20,000 hours.
Fluorescent Lighting
Before home growers had access to HID lights, fluorescent grow lights were the way to go. Inexpensive to buy, easy to hang, they do the job, but at a cost; energy usage is high compared to HID types in terms of cost per watt. Look for bulbs especially made for growing. These tend to display more blue hues and encourage leafy growth. Best for plant starts, vegetative stages and leafy plants that don’t flower. Full spectrum lights try to do it all, but there is always lumen loss. A fluorescent type grow light produces 33-100 lumens/watt, depending on the form factor and wattage with a life up to 20,000 hours. Compact models are standard Edison sockets called CFLs. Newer CFL grow lamp sizes include 125W, 200W, 250W and 300W and produce between 44-80 lumens per watt and last about 10,000 hours. Expect costs to be higher than standard non-grow bulbs.
LED Lights
A relative newcomer to the growing room are Light Emitting Diodes or LED lights. Once priced out of reach, technology has brought universal availability and huge cost reductions. The technology is rapidly changing for the better; prices have dropped as choice and quality has increased significantly. Of course, you only get what you pay for, so don’t buy a cheap Chinese knockoff expecting it to perform like the real thing. LED grow lights come in all shapes and sizes, so research is a good idea. The downside of LEDs is their output isn’t even close to that of HID bulbs, although the lack of heat output allows closer placement, thereby upping available lux to the plants.
There are some purists who say harvest yields are lower with LEDs than HIDs, but those losses are mitigated in part by lower electric costs and no need to spend money to remove excess heat as LEDs run much cooler. Lower wattage chips use passive heat sinks while higher wattage (75+) models often have heat sinks and fans. Again, do your homework to decide what lighting type is right for you. Another benefit of LED is the ability to mix chip spectrum colors and add UV chips to specific models to enhance herbal flavors.
Other Lights
It is possible to grow plants under incandescent lighting, but because the plants can’t absorb most of the light given off, and too much energy and money are wasted. For the sake of lighting, we don’t consider the use of such “Edison bulbs” unless needed to provide heat. There are better ways to get heat to your plants when needed. Their use would be best for seed propagation at best.
A plasma type grow light is prohibitively expensive and a newer technology.
Costs vs. Price
When most people think about buying hydroponic grow lights, they only think of how much the initial price will be. Unless they are handy, there will be installation costs and these costs could be substantial. The best rule of thumb for a beginner is to either buy a simple to set up kit or have a trusted tradesman if needed assist them. You may need to consult a licensed electrician if you don’t have enough properly grounded outlets. Those outlets should also be ground fault protected or GFCI. Another consideration is whether to buy top quality on some items and save on others, go all in or go cheap. It all depends of course on your budget. You can get by quite well by substituting a name brand for another quality part that won’t affect a more expensive part. Just don’t let a dollar store Velcro strap fail while holding up your $600 light rig. Think of it as insurance.
Another part of the equation is the overall cost to operate. This includes power costs, so be sure to balance the savings on that cheap tube fixture you bought over time because power costs can creep up. Because fluorescent tube life is limited to about 10,000 hours, you may need to make frequent lamp changes or purchase additional fixtures to provide the amount of lux your plants need. A single HPS bulb, even while consuming more electricity, produces the best bang for the buck in lumens and lux. A bulb that can last twice as long with proper care and can help grow two four times as many plants per cycle in a similar space is suddenly a money saver.
Of course, that cost also shows up in power consumed. Your electric bill could easily double. If you are growing a cash crop, yields may be of more importance than cost savings. In that case, first, either be experienced enough or get the information you need to succeed, because one simple stupid mistake can destroy a crop overnight. This is why it’s important to research hydroponic grow lights thoroughly to ensure they meet your budget.
Conclusion
You may use a mixture of lamp types in your grow. Some gardeners have distinctly separate areas for propagating, seed starting, cloning, vegetative growth periods and flowering stages and use several different types of lamp. Fluorescent grow lights are especially ideal for smaller plants or seedlings, as they beam continuous, bright, beams of light without creating too much heat. Best of all, most plants respond well to fluorescent lights as well, resulting in a higher growth rate. When it comes to choosing fluorescent lights, go with the usual ones found in stores and avoid the types sold as specialty growing lights, as these may not be as good a quality as normal fluorescent lights. Because the cost of the inexpensive four-foot fixture is so low, replacing the standard bulbs with one or two grow types works fine. However, if you’re growing taller plants or plants that mature at different rates, keep in mind that you’ll need to adjust the height of the lamp as they grow or move them to a better situation. LEDs can be used in conjunction in a HID grow room to enhance spectrums and for testing.
